Spectral densities angular dependence

Photoemission. In experiments such as the angular resolved photoemission spectroscopy (ARPES), one has direct access to the momentum and energy dependent one-particle spectral density... 

Fig. 3.9.4. Angular dependence of the width of the Lorentzian spectral density for mode 2 in PAA at 125 °C. Open circles denote experimental values in the [k, k configuration and open squares the values in the [k, k ] case. The curve is obtained by a least squares fit with the theory. (After the Orsay Liquid Crystals Group. )...

The time dependence of 6 and 0 are due to the reorientation of the rod and angular diffusion of the counter-ion with respect to the rod. At this stage the reorientation of the polymer rod is neglected as a slow process. Then, is determined by the modulation of the field gradient due to the time dependence of (j). The spectral density now reduces to... 

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